The present invention relates generally to cooling apparatus for use with light emitting diodes (LEDs), and more particularly to an LED lamp cooling apparatus using a thermal spay reflector for improving heat dissipation.
LEDs have been widely used in the field of illumination due to their small volume in size and high efficiency. LEDs are becoming more widely used in residential and commercial general lighting applications as the energy efficiency and cost-effectiveness of LEDs increases. In general, the light output portion of an LED is disposed within a reflector, which assists with directing the light output from the LED and increases its efficiency. Reflectors are currently made using a plastic or glass substrate that is then vacuum-coated or painted with a silvering material. These reflectors are often referred to as “second surface” reflectors as distinguished from “first surface” reflectors having a reflector surface formed of the reflector body material, for example by thermal spray techniques such as described in U.S. Patent Application Publ. 2009/0025784, which is incorporated herein by reference. Second surface reflectors are inexpensive to produce, but do not provide a thermal control function.
It is well known that LEDs generate heat when they emit light. If this heat is not quickly removed, these LEDs may overheat, and thus their work efficiency and service life can be significantly reduced, they may output at a shifted and incorrect frequency (color), pose a fire safety risk, etc. This is particularly true when pluralities of individual LEDs are arranged side-by-side in high density to form an LED lamp, such as in the aforementioned residential and commercial applications.
A traditional method of solving the heat dissipation problem is use of heat sink comprising a plurality of cooling fins attached to a base of the lamp. The heat generated by the LEDs is conducted to the cooling fins via the base, and then dissipated into ambient air by the cooling fins. However, this method is only suitable for low power consumption LED lamps, and is not suitable for high power consumption LED lamps. Furthermore, cooling fins are typically relatively large, and can limit the applications for LED lamps.
Another method of heat dissipation is using a conventional heat pipe or a loop heat pipe. The heat dissipation efficiency of these heat pipes, however, is limited by their low heat flux per unit area, and consequently these heat pipes are easy to dry out when subjected to a large amount of heat. In a further known method, a pulsating heat pipe may be employed, such as taught by U.S. Pat. No. 7,547,124, which is incorporated herein by reference. While a heat pipe is effective for heat dissipation, in each of these cases the heat pipe comprises copper or similar tubing bent and shaped to be applied to the surface of the lamp reflector. This tubing adds cost and effort to manufacturing, limits the topologies of possible cooling tube arrangements, limits the cooling pipe cross section options, increases the cost of the final lamp product, etc.
Therefore, there is a need in the art for an improved LED lamp cooling apparatus. In particular, there is a need for an improved method and apparatus that spreads heat over a large area without significantly increasing the size of a lamp package nor requiring forming and attaching elements to the lamp reflector. Still further, there is a need for an improved integrated cooling apparatus and reflector and method of making same.